This invention relates to repair of gas turbine engine components and, more particularly, to a method for restoring a chordwidth dimension of a turbine airfoil.
Conventional gas turbine engines typically include turbine sections having an alternating arrangement of rotating turbine blades and static turbine vanes. A flow of hot gases from a combustor section expands against the turbine blades and vanes to rotationally drive the turbine blades, which are coupled to an engine main shaft that drives a compressor section.
During engine operation, the hot gases produce a corrosive environment that corrosively attacks the surfaces of the blades and vanes and often results in corrosive pitting. The hot gases, soot from combustion, and particles within the flow of hot gases, also wear against the turbine blades and vanes and erode the surfaces of the blades, vanes, and other turbine engine components, which often changes the originally designed dimensions of the turbine engine components. The turbine vanes, for example, are formed in the shape of an airfoil and include a leading edge and a trailing edge that define a chordwidth there between. An aspect radio between the chordwidth and a thickness of the airfoil determines the aerodynamic efficiency of the turbine vane. Disadvantageously, the trailing edge of the turbine vane is susceptible to wear and erosion during turbine engine operation. As the trailing edge erodes, the length of the chordwidth dimension of the turbine vane decreases. Thus, the aspect ratio between the chordwidth and the airfoil thickness decreases, thereby decreasing the aerodynamic efficiency of the turbine vane.
Conventional engine component repair techniques have been used to repair component microcracks, from fatigue for example, but are undesirable for several reasons. One conventional repair method includes brazing the engine component to repair the microcracks. Typically, brazing includes heating the engine component or a relatively large zone of the engine component at high temperatures to melt a braze filler to fill the microcracks. The high temperatures may result in undesirable residual thermal stress in the engine component and undesirable changes in the metallic microstructure of the repaired areas.
Accordingly, there is a need for a method of repairing a turbine airfoil along a chordwidth dimension to restore the airfoil to an original shape and prolong the useful life of the turbine airfoil without inducing high levels of residual stress.